Bob--
In a message dated 96-09-24 08:01:12 EDT, you write:
<<
Just finished rewiring the main and dash board on my 78 MGB. Everything
works
but the directional signals, side running lights, backup lights, license
plate lights and horn. The bottom fuse on the block is always on , the
second
from the bottom is on when the key is turned on and the top two are dead
with
and without the key turned on. Prior to rewiring the fans ran whenever the
car was on not via a thermostat. Any help would be appreciated. >>
Let's break this up and see if we can't get something working here.
These
light circuits are individual, so each should be able to be corrected
independently of the others. Your wiring diagram is critical. I have
hundreds of xerox copies of my 1980 diagram (same for 78 MGBs) and I use
colored pens to trace out the circuits. You can also do well to have a
voltmeter. A circuit tester is a must. Make sure it is connected to a good
ground.
First, check the fuses. Fuse 6-7 is hot with a brown wire in/purple
out.
That should be hot at all times. Power to the running lights, license plate
lights and side lights comes from fuses 2 and 4 (red wires). Check for power
at these fuse points. If no power, check the other side of the fuse block at
terminals 1 and 3. If power, replace fuses. If no power, turn off the
battery and hook a jumper between fuse 7 and fuse 1. turn the battery back
on. The lights now work right? Disconnect the battery, disconnect the
jumper and check the light switch. That will mean dropping the wheel and
pulling off the plastic cowlings around the steering column. You may have a
defective switch.
Test the brown (power in) wire coming into the switch using the circuit
tester. If power, turn off the battery and hook a jumper from the brown wire
to the red/green wire. Red/green feeds fuse block terminals 1 and 3 and
provides the power for the side lights. Brown is power from the battery.
Reconnect the battery. You should now have running lights, side lights,
etc. parking lights, etc., and you need to replace the switch. If no power
at the brown wire, check the large four-way connector under the hood on the
right side. You should have power at that connector. If not the problem is
more serious than just no lights. The only place left to go is back to is
the battery connection on the solenoid. If no power there, the battery is
shot. REMEMBER: brown wires are always HOT.
Dinner time.
Backup lights: I just finished repairing the ones on my 1980 B, so I'm
an
expert. Locate the single connector on the right hand side under the hood.
You should have a green wire coming in and a green with brown wire out.
Make sure you have power at that point with the ignition on. If no, you
have a bad connection between the connector and the fuse block. Easy fix.
If yes, put the car in reverse with the ignition on (don’t turn over the
engine) and check for power at the connector to the right hand backup light.
If no power, crawl under the car and test for power at the switch on the
left hand side of the transmission. If you jump the switch, you should get
lights. If still no lights, check again for power at the connector. You may
have to replace it (I had a bad connector) and use a voltmeter to check for
continuity to ground. (I had a bad ground in the second fixture). If lights,
with the switch jumpd, replace the switch. Note: Once I fixed the lights,
they stayed on, indicating anotehr switch problem. Rather than messing with
the switch, I connected the green wire connector to a toggle switch in the
cockpit, then ran the other end to the green/brown wire. Now when I back up,
I throw the switch. Not that it does much good. These are the wuzziest
backup lights I’ve seen in a while.
Directionals. There are a number of places where they can go wrong.
Basically, the circuit goes like this: green wire to the hazard switch;
green from the hzd switch to the flasher; green with brown to the
directional switch on the steering column. If you don’t have power at the
light green with brown wire at the directional switch, backtrack through the
circuit until you have power. Make the correction (e.g. replace the
flasher), and move forward. If you do have power, run a jumper between the
light green with brown wire and either the green/red or green white wire at
the directional switch. You should get one side to work. Replace the
switch.
If the hazards work, then the connections to the lights are OK since the
directionals and the hazards use the same wires. If the directionals don’t
work and the hazard lights don’t work, suspect the hazard switch. Hope this
all helps. John Trifari 1980 MGB / 1955 Healey BN1
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